The recent discovery of genes responsible for the potassium leak currents, the KCNK family of potassium channels, has created the opportunity to directly target arrhythmogenic triggers of atrial fibrillation, rather than merely trying to contain them through pulmonary vein isolation. Expression of the KCNK0 gene in neurons can render these cells electrically silent by effectively shorting out any depolarizing currents. We have extended this work to demonstrate that expression of KCNK0 in cardiomyocytes renders them inexcitable. We thus propose to evaluate the KCNK0 gene for its ability to silence cardiomyocytes as a treatment for atrial fibrillation in the following specific aims: Specific Aim1: In vitro evaluation of KCNK0 for the electrical silencing of cardiomyocytes. This will involve assessment of biological effects in cardiomyocytes - establishing transfection efficiency targets, assessing cell viability, studying the electrophysiologic effects of heterogeneity from mosaic KCNK0 expression, and assessing possible cytotoxicity. Specific Aim 2: In vivo adenoviral delivery of KCNK0 to the anterior right atrium to create a line of block. This will involve linear delivery of the Ad.KCNK0 followed 5 days later by multielectrode recordings of electrical activity. Comparison of two gene delivery methods and dose response will be evaluated with assessment of gene transfer efficiency, toxicity, and protein levels. Specific Aim 3: In vivo adenoviral delivery of KCNK0 to silence pulmonary vein myocytes in a large animal model. This will involve baseline electroanatomic mapping, followed by KCNK0 gene delivery to the pulmonary veins, and then remapping of the pulmonary veins to document electrical silencing. Animals will also undergo atrial programmed stimulation and Holter monitoring to assess for proarrhythmia. Comparison will be made to Ad.GFP treated animals as well as animals treated with traditional radiofrequency pulmonary vein isolation. PUBLIC HEALTH RELEVANCE: Our primary objective is to demonstrate the feasibility of electrically silencing the pulmonary veins using gene transfer as a potential treatment for atrial fibrillation in an experimental animal model. In this project, sheep be will be used to determine whether expression of a modified potassium leak current, KCNKO, by adenoviral gene therapy approach leads to loss of electrical excitability (electrical silencing) of the cardiomyocytes investing the pulmonary vein ostia.